Vernier drive mechanism



Feb. 19, 1935. s, s. CRAM'ER 1,991,846

VERNIER DRIVE MECHANISM Filed June 2, 1934 INVENTOR ATTORNEY Patented Feb. 19, 1935 UNITED STATES PATENT OFFICE, I

Application June 2, 1934. Serial No. 72am 6Claims.

This invention relates to a vernier dri've mechanism especially useful in connection with variable condensers used in the tuning circuit of a a radio receiving set, although it may be applied to other electrical devices when coarse and fine circuit adjustments need to be made.

Before the advent of the gang condenser, that is to say, a plurality of condenser units mounted in the same frame, the fine adjustment was usually obtained by a Vernier plate which would be setto slightly vary the capacity after the coarse adjustment had been made by the regular tuning knob. However, the use of a separate vernier plate and adjusting means in a gang condenser makes the same complicated and expensive.

It is therefore the object of my present invention to be able to obtain both the coarse and fine adjustment of the adjustable portion of the condenser, such as the rotor, in a relatively simple and inexpensive manner.

A further object of my invention is to provide a fine adjustment such that persons who do not have a sensitive touch can obtain the necessary fine adjustment without difficulty.

My present invention will be readilyunderstood by reference to the annexed "drawing, wherein:

Figure 1 shows a sideselevation of a two-gang condenser with my'improvemen't applied thereto.

Figure 21s a view-of the right-hand end of the gang condenser shown in Figure 1.

' Figure 3 is a horizontal section on the line 3-3 of Figure 2 on an enlarged scale.

Figure 4 is a vertical section on the line 4-4 of Figure 2, on an enlarged scale.

Figure 5 is a section on the line H ures 1 and 3 on an enlarged scale.

of Fig- FigurefiisaviewsimilartoFiguretib tofa modified form-showing, in addition, the actuate ing devices attached to the operating shaft.

In the several views of the drawing, wherein like numbers refer to corresponding parts 1, and 2 are the end bearing plates of a two-gang condenser. ball bearing 4 in the end plate I in the manner such as disclosed in my Patent 1,800,719 issued April 14, 1931. The bearing 5 in the rear end plate 2 may be of the same type, but as illustrated, it comprises a single ball-and-socket bearing. Each of the stators 6 is carried on an insulator 7 fastened to the frame in any satisfactory manner as by rivets 8.

The rotor or main shaft 3 has a projection 9 extending beyond the end bearing plate 1. The

The rotor shaft 3 is supported by a.

signor to Radio Condenser Company, Camden extension 9 has a bore 10 terminating in an annular shoulder 11 beyond which a smaller bore 12 is provided. Passing through'the shaft extension 9 into the bore 12, is a plurality of holes to receive balls 13, three being shown in Figure 5. Preferably the holes for the balls 13 are smaller in diameter than the diameter of the balls so that the shaft 9 acts as a ball retainer whereby, in assembly operations, when the balls are dropped through the bores 10 and 12, they may be readily inserted in place as shown in several figures, that is to say, when the vernier shaft 14 is inserted into the hollow portion of the shaft I 9,the inner end of the shaft 14 forces the balls 13 into the holes made to receive them in the outer shaft 9, while the inner end of the Vernier shaft 14 is provided with a ball-race 15' which I is engaged by the balls 13. The Vernier, drive is completed by a cap 16 made of highly resilient material and, as bestshown in Figure 2, is provided with two armsor lugs 17 which preferably extend from diametrically opposite sides of the cap 16. Each of the lugs 17 has projections 18 formed therein to act as positioning means for sockets 19 formed in each of the arms 20 carried by the spring-retaining member 21 that is fastened to the end bearing plate 1 in any satisfactory manner as by a screw 22.

The cap 16 is so formed that the socket portion 23 thereof engages the balls 13 in such a manner as to press these balls against the sides of the racway 15 of the Vernier shaft 14, as well as against the walls of the holes in the main shaft 9. Furthermore, the cap 16 is so formed that it does not engage the end plate 1, a clearance space 24 being left so as to allow for further adjustment of the cap 16 by the screw 22 and the adjustable tensioning member21.

The shaft extension 9 is provided with any satisfactory operating device, such as a knob 25, which may be fastened thereto by set screw '26; also, the Vernier shaft 14 is provided with a suitable operating device such as a knob 27 fastened thereto by a set screw 28 engaging a flat surface 29 on the shaft 14. By operating the knob 25 on the shaft 9, a direct adjustment is made of the-rotor plates carried by the shaft 3 to get a coarse adjustment of the condenser.'

By turning the knob 27, the vernier shaft 14'is 5o over the knob 27, depending on the relation of the ball races with respect to each other.

' In Figure 6 the cap 16 is made somewhat differently from the cap heretofore described, in that it has two projecting arms 30 and 31 arranged diametrically opposite each other and fastened directly to the end plate 1 by screws 32. While a certain amount of adjustment can be obtained, as will be seen by reference to Figure 6, with this form of cap, I prefer the construction heretofore described. In addition, the Vernier shaft 14 is made somewhat differently in Figure 6 than in the other figures, but in general this construction functions in about the same manner as in the preferred form previously described.

What I claim is:

1. A vemier drive mechanism including a single piece main shaft hollow only for a short distance at the drive end and a vernier shaft journaled within the hollow end of the main shaft and having a raceway formed therein near the inner end thereof, a support member for the main shaft, said main shaft having holes entering the hollow end thereof, balls positioned in .said

raceway and protruding through said holes in claim 1, characterized in that the inner wall of the cap engages said balls without the cap coming in contact with the support member, and further characterized in that said means comprises a spring member carried by said support member that holds the cap in working position over the balls.

3. A vernier drive mechanism as set forth in claim 1, characterized in that the inner wall of the cap engages said balls without the cap coming in contact with'the support member, and further characterized in that the cap has a plurality of lugs disposed so pressure may be applied uniformly to the cap, said lugs having positioning means thereon, and further characterized in that said adjustable means comprises a member having resilient arms to engage said lugs to apply pressure thereto which is carried by said support member, said arms having means to cooperate with said positioning means on said lugs.

4. A vernier drive mechanism as set forth in claim 1 characterized in that said means comprises a resilient member fastened to said support H member.

5. A vemier drive mechanism comprising a pair of shafts one journaled within the drive end only of the other, a bearing support for the lastmentioned shaft end, the last mentioned shaft end having holes therein to form a cage for balls, balls seated in the cage and engaging the end of the inner shaft and protruding through said holes, and a reaction means for said balls consisting of a cap resiliently held in position over said balls and acting as a housing therefor to cause them to transmit motion from the inner shaft to the outer shaft.

6. A Vernier drive mechanism as set forth in claim 5, further characterized in that the inner shaft end has a formation such that'it is held in place by the balls against removal, as soon as the cap is held in operative position.

- STANLEY S. CRAMER; 

